In-depth understanding of the technical principles of Android Support Library View Pager framework

Android Support Library View Pages (hereinafter referred to as ViewPager) is a view control commonly used in Android development to achieve sliding switch on the page.This article will explore the technical principles of the ViewPager framework and provide relevant Java code examples. First, let's understand the basic concepts and usage of ViewPager.ViewPage can accommodate multiple sub -views, and when the user slides the screen, you can automatically switch the sub -view according to the sliding direction.ViewPager is usually used with frames to achieve page switching and management.ViewPage can achieve the sliding switching of horizontal and vertical directions, or infinite circulation sliding. The core principle of the ViewPager is implemented through the internal Scroller class and the Pageradapter class.The Scroller class is responsible for handling rolling events, while the Pageradapter class is responsible for providing sub -view data required by ViewPager. Let's take a look at the specific technical principles.First of all, by creating a custom adapter class that inherits the Pageradapter and rewritten the method, we can provide ViewPager with the required sub -view data.The following is an example: public class MyPagerAdapter extends PagerAdapter { private List<View> views; public MyPagerAdapter(List<View> views) { this.views = views; } @Override public int getCount() { return views.size(); } @Override public boolean isViewFromObject(View view, Object object) { return view == object; } @Override public Object instantiateItem(ViewGroup container, int position) { View view = views.get(position); container.addView(view); return view; } @Override public void destroyItem(ViewGroup container, int position, Object object) { container.removeView(views.get(position)); } } In the above code, we have created a custom adapter -class MyPageradapter that maintains a list containing sub -views.In the InstantiatedItem method, the sub -view is added to the sub -view by adding the sub -view to the container.In the Destroyitem method, we remove the sub -views that we no longer need. Next, we create a ViewPager object and set the custom appointment object to ViewPager.This will enable ViewPager to display and switch with the sub -view data we provide.The following is an example: ViewPager viewPager = findViewById(R.id.viewPager); List<View> views = new ArrayList<>(); // Add the sub -view to the Views list MyPagerAdapter adapter = new MyPagerAdapter(views); viewPager.setAdapter(adapter); In this example, we created a ViewPager object, and then use the custom appointed object adapter to set the ViewPager adapter.By calling the setadapter method, ViewPage can get and display the sub -view data we provide. In addition to the basic sliding switching function, ViewPage also provides many other functions, such as page indicators, page switching animations, etc.These functions can be configured by the correlation methods and attributes of the viewPager. In this article, we deeply understand the technical principles of Android Support Library View Pager framework.By achieving a custom adapter class of Pageradapter, we can provide the required sub -view data for ViewPages.With the scroll event of ViewPager, the entire framework can achieve smooth page switching effects.I hope this article will help you understand the principles and usage of ViewPager.